Dunnage bags are used in the transportation industry to brace cargo during transportation. The bags normally comprise an inner bladder of plastic, typically polyethylene, surrounded by several layers of reinforced paper. The bags are kept deflated when not in use so that they occupy relatively little space. When a cargo container is loaded with cargo, the bags are inserted into the voids between cargo, or between the cargo and the walls of the cargo container. The bags are then inflated to the desired size and pressure. The expanded bag exerts an outward pressure on the cargo, forcing the cargo against the walls of the cargo container, against other cargo, or against bulkheads. Consequently, the cargo is held in a relatively immobile state and is ready for safe transport. It is desirable to provide dunnage bags with mechanical valves adapted for quick inflation of the bags to a desired pressure.
Occasionally, dunnage bags are damaged in transit. In which case, it is desirable to have access to the interior of the bag to effect repairs, for example, by spraying sealant on the interior surface of the bag.
Inflation of the bags is typically accomplished through a valve that is attached to the bag surface. A hose is coupled to the valve and conveys pressurized gas, typically compressed air, through the valve and into the bag. When the bag reaches the desired inflation pressure, the hose may be removed, and the valve closed to prevent air from escaping.
Dunnage bag valves may be simple one-way valves. Such valves typically have a flapper seal kept in a shut position by a biasing spring force that allows air into the bag but not out of the bag. A disadvantage of this design is that the valve cannot be locked shut to prevent air from entering or exiting the bag, and cannot be locked open to allow air to enter or exit the bag. Such valves may require manual force to be exerted against the spring to deflate the bag.
Previously, some dunnage bag valves allowed air to flow into and out of the bag, but were not designed to be removed from the bag so that the interior of the bag could be accessed to effect repairs to the bag. Other valve designs have two pieces so that one piece can be removed from the other to allow access to the interior of the bag. A first piece ("plug") threads into a second piece ("collar"). The collar is mounted to the bag. When the plug is unscrewed completely it comes apart from the collar, exposing an orifice through which air can flow into or out of the bag (this is how deflation of the bag is achieved with such valves). In such valves, removing the plug from the collar also allows access to the interior of the bag to perform repairs on the bag. The plugs of such valves are easily lost or stolen because they are removable from the collar. To prevent loss of the plugs, some of the these valves connect the plug to the collar with a chain. However, the chain may become entangled when the valve is in operation. Also, the chain may make it difficult to attach an air hose to the valve to inflate the bag. Further, the plug may be lost or stolen in spite of the connecting chain if the chain is accidentally or deliberately severed. If the plug becomes detached from the collar, the plug may fall into the cargo being transported. In some instances, plugs lost in this way have caused serious damage to machinery that is subsequently used to handle the cargo.